The invention herein generally relates to a miniature electroacoustic instrument and, in particular, a peritympanic hearing instrument suitable for use in humans.
Hearing instruments typically are custom-designed to suit the anatomical and audiological needs of an individual user. Because custom-made devices can be very costly, it is desirable to mass-produce a hearing instrument that is relatively inexpensive and is readily adaptable to most users' anatomical and audiological requirements, and which is inconspicuous and lightweight.
There are significant challenges associated with the development of mass-produced hearing instruments. Although the structure of the external auditory canal generally is a sinuous, oval cylinder with three sections, it can vary significantly depending on the particular individual. Traversing the outer canal towards the inner tympanic membrane, the first section is directed inward, forward, and slightly upward. The next section tends to pass inward and backward. The final section is carried inward, forward, and slightly downward. The outer portion of the ear canal is surrounded by cartilaginous tissue, with the inner portion being surrounded by bone. The canal is formed with a very thin lining of skin, which is extremely sensitive to the presence of foreign objects. Further details of the path and contours of the external auditory canal are described in U.S. Pat. No. 4,870,688, issued to Barry Voroba et al., and in U.S. Pat. No. 5,701,348, issued to Adnan Shennib, both of which are incorporated herein by reference.
U.S. Pat. No. 4,870,688 describes an in-the-canal miniaturized hearing aid contained within a prefabricated ear shell assembly composed of a hollow rigid body with a soft, resilient covering fixed to its exterior. The microphone, receiver, amplifier, and battery are all wholly contained within a prefabricated modular sound assembly which snaps into a patient-selectable prefabricated ear shell assembly. The soft, resilient covering that is affixed to the exterior of the rigid core is intended to allow the cylindrical or elliptical shape of the in-the-canal hearing aid to more easily conform to the individual variations in a user's auditory canal.
U.S. Pat. No. 5,701,348 described a hearing device having highly articulated, non-contiguous parts including a receiver module for delivering acoustic signals, a main module containing all of the hearing aid components except the receiver, and a connector that is articulated with both the receiver module and the main module to permit independent movement of the receiver and main modules. Separation of the receiver from the main module, and the receiver's articulation with respect to the main module, is intended to provide at least two degrees of freedom in movement and independent movement of the receiver module with respect to the main module, and visa versa.
Attempts have also been made to provide inserts intended to be used as a part of a hearing aid device. U.S. Pat. No. 2,487,038, issued to Jasper Baum, describes an ear insert shaped for insertion into the concha or the outer cavity of an ear. It includes a series of ball-shaped ball-like wall sections each made with sufficiently thick walls so as to give them great stiffness and prevent substantial distortion of the cross-section of the sound-passage portions extending therethrough under the action of external bending forces when the insert is inserted into the curved space of the outer ear cavity. The ball-like wall sections are interconnected by short neck-like sections to readily flex and take up substantially the entire deformation to which the channel insert is subjected. Thin flexible, skirt-like protrusions in outward and rearward directions from the ball-like wall sections to become wedged against the surrounding surface portions of the outer ear cavity for automatically establishing therewith an acoustic seal.
U.S. Pat. No. 3,080,011, issued to John D. Henderson, describes an ear canal insert with a very soft tip with flanges. A flexible mounting tube is considerably stiffer than the material of which the head portion flanges are formed so that it can be used to force the insert portion of the device into the ear canal.
U.S. Pat. No. 5,201,007, issued to Gary L. Ward et al., describes earmolds that convey amplified sound from the hearing aid to the ear. An acoustic conduction tube extends into the ear canal and a flanged tip on the conduction tube creates a resonant cavity between the tip and the tympanic membrane. The tip is constructed of a flexible material to form a sealed cavity adjacent the tympanic membrane, permit the seal to be obtained with only slight pressure against the wall of the ear canal, and permit the tip to be oscillated by the natural, unamplified sounds which arrive by air conduction through the ear canal, so that the oscillation can raise the resonant frequencies of the cavity.
U.S. Pat. No. 5,185,802, issued to Mark F. Stanton, describes a modular hearing aid system comprising a customized exterior shell formed of compliant material, in situ, in the usual manner in accordance with the shape of the ear canal of the individual user, such that a separate and distinct shell is required for each ear. A housing containing the hearing aid components is removably inserted in the shell. The housing has a bilateral standardized shape so it can be used with either a right or left ear customized shell.